Field of the Invention
The invention relates to a method and a test structure for determining a plurality of interconnected resistors formed as an integrated circuit. For the purpose of enabling a four-point measurement, the resistors have measurement pads via which they can be supplied and measured.
In the fabrication of integrated circuits disposed as chips in rows and columns on a wafer, it has already been known to provide test structures at which various process parameters can be checked and monitored. The test structures include, for example, electronic components such as transistors, resistors or the like, at which the various process parameters can be checked at least in randomly sampled fashion. Such test structures are necessary since the integrated circuits are generally constructed with such complexity that the process parameters cannot be tested at the circuits themselves.
In this connection, it is known, moreover, to test resistors arranged in the form of series resistors. In this case, low-value resistors, in particular, are connected by means of measurement pads which allow a Kelvin contact-connection according to the four-point measurement method. In this measurement method, each resistor respectively requires two measurement pads for each connection. Since, in the development of integrated circuits, it is always endeavored to make the circuits as small as possible for technological and economical reasons, the high number of measurement pads is disadvantageous since these pads require a comparatively large amount of space. In particular, the arrangement of the test circuits in the sawing frame (kerf) between the chips is difficult since the latter is very narrow. However, even with an arrangement on a test chip, the available chip area on the wafer is occupied in an unfavorable manner.
German published patent applications DE 36 15 550 A1 and DE 100 12 313 A1 have previously described resistance measuring arrangements in which a ring-type arrangement of resistors is provided.